docs: def distinct(self, field=None):
          """
          If field is None, then it means that it'll create:
              select distinct *
          and if field is not None, for example: 'name', it'll create:
              select distinc(name), 
          """
          if field is None:
              self.funcs.append(('distinct', (), {}))
          else:
              self.distinct_field = field
          return self